Windmills which generate electricity by harnessing wind power have existed for several decades. Existing designs generate electrical power, but the cost of this power has generally been uncompetitive with electricity generated by burning fossil fuels. Electricity generated through wind power usually costs more than twelve cents per kilowatt-hour, on a wholesale basis. Electricity generated by burning fossil fuels,
by contrast, costs around 8 cents per hour. Inventors have therefore tried to create electricity-generating windmills that can generate a larger amount of electrical energy from the same amount of wind energy. Other inventors have attempted to create electricity-generating windmills with parts in configurations that are different from electricity-generating windmills of the standard design.
Much of the electrical power generated in the world today is generated through power plants which bum fossil fuels, namely oil, coal, and natural gas. The Earth's supply of fossil fuels is finite, and, in addition, combustion of fossil fuels has other drawbacks, such as emissions of carbon dioxide and particulate matter. These problems have become more urgent in recent years, because of the increase in oil prices, and because of mounting global concern about greenhouse gas emissions.
Utilities and individuals have launched an effort to create other, less polluting ways of generating electricity. “Renewable” sources of electrical power include wind power, solar power, and other sources. Wind power is generally harnessed through windmills that generate electricity. When the wind blows, it causes the rotor blades of the windmill to turn, which drives a turbine, which is connected with one or more generators, which generate electricity.
General Principles Governing the Amount of Electricity Generated by a Windmill
There is a strong positive correlation between the amount of wind energy captured by the windmill and the amount of electrical power which can be generated by the generators connected with the windmill, for any given electricity-generating windmill. Therefore, the more wind energy is captured by the windmill, the more electricity the generators connected with the windmill will be able to generate, until the generators reach their maximum capacity. The general rule is that a portion of the energy contained within the wind is captured when it hits the blades, which are less than 100% efficient. A portion of the energy captured by the blades then goes to the turbine, which is also less than 100% efficient. Finally a portion of the energy which reaches the turbine then is transmitted to the generators, which are also less than 100% efficient. The generators then generate electricity.
The speed at which the wind is blowing is proportional to the energy within the wind, and therefore, more electrical energy can theoretically be generated from wind traveling at faster speeds.
The equation governing the kinetic energy of the wind hitting a wind-powered turbine's blades iske=½mv2 where ke=kinetic energy, m=mass and v=velocity.
Thus, absent other considerations, a twofold increase in the wind speed of wind hitting the blades of a rotor of a windmill will result in a fourfold increase in the amount of wind energy imparted to the blades of that windmill.
The power output of an electricity-generating windmill is also directly related to the windmill's total blade area. A twofold increase in the total surface area of the blades will result in a twofold increase in the amount of wind hitting the blades, and therefore, will result in a twofold increase of the amount of wind energy imparted to the blades of that windmill, if all other factors are equal.
Other factors may vary, which will cause some variation in the increased amount of power that a windmill actually generates in the above scenarios. For example, each blade sometimes creates a small amount of turbulence in the air, which may affect the amount of electricity generated by the other blades of the windmill. However, the above rules are useful guidelines for calculating the amount of electrical energy that a given windmill has the ability to produce;
Therefore, as a general rule, a windmill will generate more energy if it utilizes higher-speed winds, and will also generate more energy if it has wider blades. The capacity of the turbines and generator connected to the windmill are also relevant factors. Larger numbers of generators, and higher-capacity generators, will be able to convert a greater amount of kinetic energy to electrical energy.
Another limitation of electricity-generating windmills of the prior art is that the generator(s) are placed at or near the conventional center (5) of a prior art electricity-generating windmill. This limits the size of the generator(s) which can be included as part of a prior art electricity-generating windmill, because more and/or larger generators are heavier. Therefore, when placed at or near the conventional center (5), they will make the conventional windmill (4) less stable, and will increase the risk of the conventional windmill (4) collapsing or falling over in high winds. The ability of conventional windmills (4) to create electrical energy is therefore limited by the lack of generators to utilize the energy carried by the wind power hitting the conventional windmills' (4) blades. The present invention solves this problem by allowing the generators to be placed at ground level, or below ground. Therefore, the number, size, capacity of such generators can be increased indefinitely, as needed. The stability of the machine of the present invention will not be affected by this.
The Venturi Effect and its Relevance to Wind Power
The Venturi Effect has been known since 1797. The Venturi Effect is that, as a fluid passes through a constricted tube, the fluid's velocity must increase, and its pressure must decrease. The equation governing this is as follows:p1−p2=d/2((v2)2−(v1)2)Where p1 is the fluid pressure at the wider opening, p2 is the fluid pressure at the narrower opening, d is the density of the fluid, v2 is the fluid velocity when the pipe is narrower, and v1 is the fluid velocity when the pipe is wider.
The Venturi effect can be used to increase the speed of a boat or other watercraft, which is connected to a constricted tube, because of the increase in velocity and decrease in pressure of the water as it passes through the tube. Some hydrofoil boats use the Venturi effect to increase their speed.
An effect similar to the Venturi effect applies to air and other gases, in that as a gas passes through a constricted tube, where the tube is narrower at some points than others, the gas's velocity must increase, and its pressure must decrease, at the narrower points.
This has important implications for the ability of windmills to generate electricity. If the wind passing through a windmill's blades has a higher velocity, then the kinetic energy hitting the windmill's blades will be higher, as noted above. The windmill will therefore be able to generate more electricity, as explained above. Some embodiments of the present invention employ a “shroud” with openings that are wider than the diameter of the blade rotors. This shroud constricts the air as it passes through the windmill's rotors, and increases the velocity of that air. This then increases the energy of the wind passing through the rotors, enabling the windmill to ultimately generate more electricity.
Other embodiments of the present invention shape the shroud like a nozzle, which also constricts the air as it passes through the windmill's rotors, increasing the kinetic energy of that air, which then hits the blades, enabling the windmill to ultimately generate more electricity.
Still other embodiments of the present invention use a lightweight, thin, metal nozzle to constrict the air as it passes through the rotors.